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How Many of Pi’s Digits Should We Use?

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Engineers, mathematicians, and scientists alike use pi a lot as part of work. It is that constant which is defined as the ratio of a circle’s circumference to its diameter with an approximate value of 3.14159.

Did you cringe at how the value of pi is displayed above? Is it too long for you? Perhaps too short? Well, for some guy in India, it is way too short – he recited 70,000 digits of pi blindfolded in front of a panel and got a world record for it.

But for the regular use of pi, thousands of digits could be exhausting just to say that we are being accurate. So what is the ‘right’ number of decimal places that should we use in everyday computations?

Maybe this has been answered by the NASA-Jet Propulsion Laboratory scientists and engineers, after one fan on Facebook was curious about it and asked if how many decimals of the mathematical constant pi they use.

This was the question:

Does JPL only use 3.14 for its pi calculations? Or do you use more decimals like say: 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360

Someone from the NASA-JPL replied through its website and shared the answer of director and chief engineer for NASA’s Dawn mission, Marc Rayman.

He started his answer with a short story about a boy in his sixth grade who was into space and later became involved in space exploration and with a doctorate in physics.

It was Marc Rayman himself.

Photo via RocketSTEM

He went on, “To start, let me answer your question directly. For JPL’s highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793. Let’s look at this a little more closely to understand why we don’t use more decimal places.

“I think we can even see that there are no physically realistic calculations scientists ever perform for which it is necessary to include nearly as many decimal points as you present.”

Rayman gave three stellar examples to defend his answer, which can be found here.

Would you memorize the 15 decimal places to follow an authority? Or would you stick with the 3.14159 for its simplicity?


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